Structs and mutating functions

I haven't used structs much. It seems to be a bit odd with requiring didSet and mutating.

The biggest blocker for me is that you can't assign anything to the variables inside a closure, as self is immutable in structs.

Here's a way to essentially have an observer set up, so that you can keep the struct if you didn't want a class.

struct Thing {
    var stuff: Int
    mutating func update(stuff: Int) {
        self.stuff = stuff
    }
}

var thing: Thing? {
    didSet {
        print("Mutating: \(thing?.stuff)")
    }
}

thing = Thing(stuff: 0)
thing?.update(stuff: 1)
thing?.update(stuff: 2)